"Operations Freshman and Grouse

Destruction of the plant was mounted by the Combined Operations command in November 1942. The plan consisted of two operations: the first would drop a number of Norwegian locals into the area as an advance force, and once in place a party of British engineers would be landed by glider to attack the plant itself.

On 19 October1942, a four man team of Special Operations Executive (SOE) trained Norwegian commandos parachuted into Norway. From their drop point in the wilderness they had to ski a long distance to the plant, so considerable time was given to complete this part of the mission, known as Operation Grouse. This plan, unlike those which did not succeed before, included the team studying and memorising blueprints.

Once the Norwegian Grouse team managed to make contact with the British, the British were suspicious, as they had not heard from the SOE team for a long time: they had been dropped at the wrong place, and had gone off course from there several times. The secret question took the form of: "What did you see in the early morning of (a day)?" The Grouse team replied: "Three pink elephants." The British were ecstatic at the success of Norwegian team's injection, and the next phase of operations commenced.

On 19 November1942, Operation Freshman followed with the gliderborne landing on frozen lake Møsvatn near the plant. The two Airspeed Horsa gliders, towed by Handley Page Halifax bombers, each carrying two glider pilots and fifteen Royal Engineers of the 9th Field Company, 1st British Airborne Division, took off from RAF Skitten near Wick in Caithness. The towing of gliders had always been a hazardous profession, but these circumstances were made worse by the long flying distance to Norway and poor weather conditions which heavily restricted visibility. One of the Halifax tugs crashed into a mountain, killing all seven aboard; its glider was able to cast off, and it crashed nearby, resulting in several casualties. The other Halifax successfully delivered its charge to the area of the landing zone, but although the conditions had substantially improved it was impossible to locate the landing zone itself due to the failure of the link between the Eureka (ground) and Rebecca (aircraft) beacons. After much endeavour and with fuel running low, the Halifax pilot decided to abort the operation and return to base. However, shortly afterwards, the tug and glider combination encountered heavy cloud and in the resulting turbulence the tow rope broke. The glider made a crash landing, not far from where the other glider had come down, similarly inflicting several deaths and injuries. The Norwegians were unable to reach the crash sites in time, and the survivors quickly came into the hands of the Gestapo, who tortured them during interrogation (not sparing the badly injured) and later had them executed under Hitler's Commando Order.

The Norwegian Grouse team thereafter had a long arduous wait in their mountain hideaway, subsisting on moss and lichen during the winter until, just before Christmas, a reindeer was caught.

A 1948 Norwegian movie based on this raid, called Kampen om tungtvannet, features performances by at least four of the original participants in the raid.

Operation Gunnerside

British command was aware of the "success" of the Grouse team, and decided to build another operation in concert with them. By this time the original Grouse team were being referred to as Swallow. In February 1943, in Operation Gunnerside (named after a village and the moor where the Hambro Family and Sir Charles Hambro, the head of SOE, used to shoot grouse), an additional six Norwegian commandos were dropped into Norway by a Halifax bomber of 138 Squadron from RAF Tempsford. They too were successful in landing, and found the Swallow team after a few days of searching. The combined team then made final preparations for their assault on the night of 27 February.

Supplies required by the commandos were dropped with them in special CLE containers. (One of these was buried in the snow by a Norwegian patriot to hide it from the Germans; he later recovered it and in August 1976 handed it over to an officer of the Army Air Corps, who were exercising in the area. The container was brought back to England and is now on display at the Airborne Museum at Aldershot.)

Following the Freshman attempt, mines, floodlights and additional guards were set around the plant. Whilst the mines and lights remained in place, security of the actual plant had slackened somewhat over the winter months. However, the single 75-metre bridge spanning the deep ravine, 200 metres above the River Maan, was well guarded.

The force elected to descend into the ravine, ford the icy river and climb the steep hill on the far side. The winter river level was very low, and on the far side, where the ground leveled, they followed a single railway track straight into the plant without encountering any guards. Even before Grouse landed in Norway, SOE had a Norwegian agent within the plant who supplied detailed plans and schedule information. The demolition party used this information to enter the main basement by a cable tunnel and through a window.

The saboteurs then placed explosive charges on the heavy water electrolysis chambers, and attached a fuse allowing sufficient time for their escape. Other than the night watchman, whom they had to "silence", no one interfered with their mission, nor intercepted their escape. A British machine gun was purposely left behind to indicate that this was the work of British forces and not of local resistance, in order to prevent reprisals. The explosive charges detonated, destroying the electrolysis chambers and releasing the stocks of heavy water.

All ten made good their escape whereafter six skied 400 kilometres to Sweden and four remained in Norway for further work with the resistance. The plant was restored by April and SOE concluded that a repeat raid would be extremely difficult, as German security was thereafter very considerable. In November the plant was attacked by a massed daylight bombing raid of 143 B-17 bombers dropping 711 bombs, of which at least 600 missed the plant. The damage, however, was quite extensive; the reason for the original ground assault a year earlier was that the available alternative of night bombing was considered unrealistic at that time.

Aftermath

While this attack did little damage to the plant, it did stop production for a short period. Almost as soon as production re-started, the USAAF started a series of raids on it. The Germans were convinced that this would eventually result in some "hits", and they decided to abandon the plant and move remaining stocks and critical components to Germany in 1944.

Knut Haukelid discovered their plan and decided to sabotage a ferry carrying the heavy water across lake Tinnsjø. He recognised a crew member and talked to him, taking this advantage to slip into the bottom of the ship and plant the bomb, after which he escaped. Eight and half kilograms of plastic explosive with two alarm-clock fuses were fixed to the keel of the ferry, D/F Hydro, which was to carry the railway tankers of the water. On 20 February1944, shortly after setting off around midnight, the ferry and its cargo sank in deep water, finally capping the original mission's objective and halting Germany's atomic bomb development programme. A number of Norwegian civilians were killed as the ferry sank. Witnesses reported seeing barrels floating after the sinking, leading to speculation that they did not really contain heavy water. But an examination of records after the war showed that some barrels were only half full, and therefore would have floated. A few of these may have been salvaged and transported to Germany. Around 2005, an expedition retrieved a barrel (numbered "26") from the bottom of the lake. Its concentration of heavy water matched the records, and confirmed that the shipment was not a decoy.

Unknown to the saboteurs, a "Plan B" had been set up by the SOE, who arranged a second team to attack the shipment at Herøya should the first attempt fail. The disassembled factory was later found in southern Germany during the closing stages of the war by members of Operation Alsos nuclear seizure force.

With the benefit of hindsight, the consensus on the German wartime nuclear program is that it was a long way from producing a bomb, even without the sabotage. Nevertheless, the feats of the Norwegian saboteurs have made them national heroes."